Influence of plasticity index on sub-base material : experimental review

Abstract

Major parts of the Eastern and Northern Provinces of Sri Lanka are covered wi cohesionless soil. These locally available cohesionless soils have been utilized for construction of su base in road constructions. Recently cracks, settlement and outward movement have been observed' - the certain pavements constructed in the north and east. It is suspected that the poor plastic properti of locally available soil would have caused this failure. Objective of this paper is to identify tne influence of Plasticity Index on sub-base material properties and review the applicability of th current specifications for selection of low plasticity soil as Sub-base materiaL Based on the collecte information, a comprehensive laboratory tests program was formulated to investigate tinterrelationships between the soil properties such as grading, maximum dry density, CBR valu Plasticity Index, and Liquid Limit by mixing different type of clays with pure coarse sand (Ri Sand). Relationships between CBR Vs Plasticity Index and MDD Vs Plasticity Index have b established for a fine grade sub-base materiaL It was found that CBR is low at both low and hi plasticity soil. ICTAD specification specified upper limit for Plasticity Index has been verified in} experimental study. Experimental results emphasised the need of establishing a lower limit fort' Plasticity Index in selection of sub-base materiaL